Electromagnetic styluses are known in the art for use and control of a digitizer. Position detection of the stylus provides input to a computing device associated with the digitizer and is interpreted as user commands. Position detection is performed while the stylus tip is either touching and/or hovering over a detection surface of the digitizer. Often, the digitizer is integrated with a display screen and a position of the stylus over the screen is correlated with virtual information portrayed on the screen.
U.S. Pat. No. 5,571,997 entitled “Pressure sensitive pointing device for transmitting signals to a tablet” the contents of which is incorporated herein by reference, describes a pressure sensitive pointing device or pen for use with an electronic tablet that determines the position of the pointing device on the surface of the tablet. The pointing device incorporates a variable reluctance circuit responsive to the force exerted on the pen point for modulating a radiating frequency, emanating from the pen, in proportion to the force.
U.S. Pat. No. 7,292,229 entitled “Transparent Digitizer” which is assigned to N-trig Ltd., the contents of both which is incorporated herein by reference, describes a passive electro-magnetic stylus which is triggered to oscillate at a resonant frequency by an excitation coil surrounding a digitizer. The oscillating signal is sensed by the digitizer. The stylus operates in a number of different states including hovering, tip touching, right click mouse emulation, and erasing. The various states are identified by dynamically controlling the resonant frequency of the stylus so that the stylus resonates at a different frequency in each state. A position of the stylus, e.g. the stylus' tip with respect to the digitizer sensor is determined based on signals sensed from sensor.
U.S. Patent Application Publication No. 20080128180 entitled “Position Detecting System and Apparatuses and Methods for Use and Control Thereof” assigned to N-Trig Ltd., the contents of which is incorporated herein by reference, describes a stylus that emits an oscillation frequency that can be picked up by a digitizer sensor and used to determine its position on the sensor. The stylus includes a variable element, e.g. a resistor, capacitor, or an inductor, that is responsive to pressure exerted on the stylus tip by the user and triggers changes in the frequency emitted by the stylus. The digitizer system is operable to discern between different frequencies emitted by the stylus to determine a position of the stylus and a pressure exerted on the stylus tip by the user.